Use of RSSI indication for improved data transmission over amps network

ABSTRACT

A method of using control channel information is provided to enhance data throughput of a cellular communication system. The cellular communication system includes a single system control unit coupled to a data pump, a cellular transceiver and a radio transceiver. A method of operating the cellular communication system includes the following steps: (a) detecting a control channel signal indicating that a channel interruption is to occur; (b) decoding the control channel signal; (c) sending the decoded control channel signal to the system control unit; (d) controlling the parameters of the adaptive components of the data pump so that the parameters remain at a converged state or are adjusted even during the channel interruption; (e) interrupting the channel; and (f) re-establishing the channel within a reduced retraining time period. Before interrupting the channel, the cellular communication system may also transmit a command to a data pump of a second remote modem so that the remote modem can initiate an appropriate process to maintain the parameters off its adaptive components at a converged state or to adjust the parameters continuously during the channel interruption. The cellular communication system may also acknowledge receiving the control channel signal before the channel is interrupted.

RELATED APPLICATION(S)

This application is a continuation-in-part of application Ser. No.08/414,907, entitled "Use of Control Channel Information to Enhance DataThroughput of an Integrated Cellular Communication System invented by N.Goplalan Nair, assigned to the assignee of the present invention andfiled Mar. 31, 1995.

BACKGROUND OF THE INVENTION

(1)Field of the Invention

The present invention relates to wireless communications systems, andmore particularly to data and voice communications systems utilizing anadvance mobile phone system (AMPS) cellular network.

(2) Description of the Related Art

Referring to FIG. 1, to provide communications over a telephone network,a data communication network system includes a computer host 12 and amodem 14 that is connected to a wall socket of a phone line so that datafrom modem 14 can be transmitted to a telephone network 16. A secondmodem 18 is provided to receive the data from modem 14. Modem 18receives the data from telephone network 16 and sends it to a computerhost 20. The system shown in FIG. 1 is a typical data communicationnetwork system for a wired telephone network.

A conventional wireless communication network system is shown in FIG. 2.The wireless network system includes a computer host 22, a modem 24, amodem interface 26, a cellular phone 28, and a base station 30. Thewireless system is typically coupled to telephone network 16, modem 18and computer host 20. In this instance, modem 18 is a landline modem. Inanother instance, telephone network 16 may be replaced by a cellularphone and a modem interface in which modem 18 is a mobile modem. Totransmit data from computer host 22 to computer host 20, the data incomputer host 22 is sent to cellular phone 28 through modem 24 and modeminterface 26. Cellular phone 28, in turn, transmits the data to basestation 30. Base station 30 then transmits the data to telephone network16 which sends the data to computer host 20 through modem 18. Becausemodem 24 of FIG. 2 is the same as modem 14 of FIG. 1, modem interface 26is required in the network system shown in FIG. 2. Because of modeminterface 26, node 25 has the same characteristics as node 15 of FIG. 1.Modem interface 26 provides an analog path with appropriate protocols tomake cellular phone 28 and base station 30 appear as a landlinetelephone network. Modem interface 26 is used to convert the signal atnode 25 which is outputted by modem 24 into a signal that is compatiblewith cellular phone 28. Also, modem interface 26 converts the signaloutputted by cellular phone 28 at node 27 into a signal that iscompatible with modem 24. For instance, when computer host 22 tries todial a number, modem 24 produces a tone dialing signal at node 25.However, cellular phone 28 cannot accept the tone dialing signal as aninput. Thus, modem interface 26 converts the tone dialing signal intoanother form that can be received by cellular phone 28.

In FIG. 2, modem 24 can be made internal or external to computer host22. Modem interface 26 can be an external device or an internal devicebuilt into modem 24 or cellular phone 28.

FIG. 3a is a detailed block diagram of modem 24, modem interface 26 andcellular phone 28 of FIG. 2. Modem 24 includes a system control A 43, ahost interface 42, a data pump 44, a digital-to-analog (D/A) andanalog-to-digital (A/D) converter 45, and a data access arrangement(DAA) 46. System control A 43 controls and operates host interface 42,data pump 44, D/A & A/D converter 45 and DAA 46. Data pump 44 modulatesdata coming from computer host 22 of FIG. 2 and demodulates signalscoming from cellular phone 28. The D/A is used to convert digitalsignals from data pump 44 into analog signals, and the A/D is used toconvert analog signals coming from cellular phone 28 into digitalsignals for data pump 44. DAA 46 is used as a protective connectingdevice that serves as an interface between D/A & A/D converter 45 andmodem interface 26.

Cellular phone 28 in FIG. 3a includes a system control B 53 forcontrolling and operating the components in cellular phone 28--an analogcellular transceiver 50 and a radio transceiver 52. To send data, analogcellular transceiver 50 receives analog signals from modem interface 26,processes the signals in an analog domain and generates signals that canbe converted into radio waves. To receive data, radio transceiver 52receives radio waves, converts the radio waves into analog signals sothat analog cellular transceiver 50 can process them in the analogdomain.

The wireless communication system shown in FIG. 3a has severaldisadvantages. First, because the wireless communication system uses ananalog cellular transceiver whose characteristics are optimized forvoice communication but not for data communication, data communicationrate is low. Second, because a signal conversion (i.e.,analog-to-digital or digital-to-analog) occurs between two signalprocessing units (data pump 44 and analog cellular transceiver 50),signals tend to degrade, causing errors. Ideally, all signals should beprocessed in one domain (e.g., either digital or analog), and beconverted into another form either at the beginning or at the end of thesignal processing to avoid signal degradation. In the system shown inFIG. 3a, to send data, data pump 44 processes digital signals, D/A & A/Dconverter 45 converts the digital signals into analog signals, andanalog cellular transceiver 50 processes the analog signals that aredegraded. When signals are converted from a digital to an analog form(or from an analog to a digital form), the signals become degradedbecause the conversion process loses some information in the signals,and noise is injected into the signals. When the degraded signals areprocessed further, they may further reduce performance. Third, becausemodem 24 and cellular phone 28 operate under two separate systemcontrols, modem 24 cannot adapt to dynamic changes that occur incellular phone 28, and cellular phone 28 cannot adapt itself to thechanges that occur in modem 24. A wireless communication system shown inFIG. 3a which is connected to an AMPS cellular network allows only themodem analog data and the emulated PSTN type information (ringing, busy,etc.) to be transferred between modem 24 and cellular phone 28. Ineffect, modem 24 sees the cellular telephone channel as a landlinetelephone channel. In addition, currently existing cellular protocolssuch as NMP10 and ETC are blind to the dynamic characteristics of thecellular telephone channel.

A prior art wireless communications system shown in FIG. 3b is similarto the one shown in FIG. 3a except that it uses a digitally implementedcellular transceiver 72 instead of an analog cellular transceiver.Because cellular transceiver 72 is digital, it may process signals moreaccurately than analog cellular transceiver 50. However, because thewireless communication system uses digital implementation, the systemrequires two extra A/D & D/A converters. Thus, the system in FIG. 3b mayrequire more hardware than the system shown in FIG. 3a. The system inFIG. 3b has similar disadvantages as the one shown in FIG. 3a. Becauseof D/A & A/D converters 65 and 70, digitally implemented cellulartransceiver 72 receives and processes degraded signals. Data degradationmay be greater in this instance because the system requires twoconversions to send signals from data pump 64 to digitally implementedcellular transceiver 72. In addition, like the system in FIG. 3a, thesystem in FIG. 3b includes two system control units: system control A 63for modem 24 and system control B 73 for cellular phone 28. Becausemodem 24 and cellular phone 28 are controlled by two separate systemcontrols, as described before, modem 24 cannot adapt to the dynamicchanges that occur in cellular phone 28, and cellular phone 28 cannotadapt to the changes that occur in modem 24.

It will be advantageous, therefore, to provide a wireless communicationsystem (a) having one system control unit for all the components of thesystem so that the various components of the system can be adapted andadjusted as the parameters of the other components or the dynamiccharacteristics of the cellular channel vary and (b) performing all ofthe signal processing in one domain to reduce signal degradation. In thepresent invention, a wireless communication system operating under onesystem control unit provides a way to implement advanced protocols thattake advantage of control channel information and messages that arepassed between a base station and a cellular transceiver.

BRIEF SUMMARY OF THE INVENTION

The present invention provides methods of using control channelinformation of an integrated cellular communication system to enhancedata throughput. The cellular communication system of the presentinvention includes a system control unit coupled to a data pump, acellular transceiver and a radio transceiver.

One method of operating the cellular communication system in accordancewith the present invention includes the following steps: (a) detecting acontrol channel signal indicating that a channel interruption is tooccur; (b) decoding the control channel signal; (c) sending the decodedcontrol channel signal to the system control unit; (d) controlling theparameters of the adaptive components of the data pump so that theparameters remain at a converged state; (e) interrupting the channel;and (f) re-establishing the channel within a reduced retraining timeperiod. Before interrupting the channel, the cellular communicationsystem may also transmit a command to a data pump of a second cellularcommunication system so that the second system can initiate anappropriate process to maintain the parameters of its adaptivecomponents at a converged state. The cellular communication system mayalso acknowledge receiving the control channel signal before the channelis interrupted.

Another method of operating the cellular communication system inaccordance with the present invention includes the following steps: (a)detecting a control channel signal indicating that a channelinterruption is to occur; (b) decoding the control channel signal; (c)sending the decoded control channel signal to the system control unit;(d) continuously adjusting the parameters of the adaptive components ofthe data pump so that the parameters are adjusted even during thechannel interruption; (e) interrupting the channel; and (f)re-establishing the channel within a reduced retraining time period.Like the first method, the cellular communication system may alsotransmit a command to a second cellular communication system andacknowledge the control channel signal before the channel isinterrupted.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects, features and advantages of the present invention will beapparent from the following detailed description wherein:

FIG. 1 is a block diagram of a prior art data communications networksystem for a wired telephone network.

FIG. 2 is a block diagram of a prior art wireless communications networksystem.

FIG. 3a is a detailed block diagram of a portion of the wirelesscommunications network system shown in FIG. 2 having an analog cellulartransceiver.

FIG. 3b is a detailed block diagram of a portion of the wirelesscommunications network system shown in FIG. 2 having a digitallyimplemented cellular transceiver.

FIG. 4 is a digital wireless communication system operating under onesystem control unit according to the present invention.

FIG. 5 is a detailed block diagram of the data pump of FIG. 4.

FIG. 6 is a block diagram of the digitally implemented cellulartransceiver of FIG. 4.

FIG. 7a is a graph showing the relationship between an input and anoutput of a compression function used for audio signals.

FIG. 7b is a graphical relationship between an input and an output of acompression function used for data signals according to the presentinvention.

FIG. 8a is a graph illustrating the relationship between an input and anoutput of an expansion function used for audio signals.

FIG. 8b is a graphical relationship between an input and an output of anexpansion function used for data signals according to the presentinvention.

FIG. 9a is a flow chart illustrating one method of using control channelinformation to enhance data throughput of a wireless communicationsystem according to the present invention.

FIG. 9b is a flow chart illustrating another method of using controlchannel information to enhance data throughput of a wirelesscommunication system according to the present invention.

FIG. 10 is a computer system that may utilize a wireless communicationsystem in accordance with the present invention.

FIG. 11 is a graph of the RSSI signal as a function of time whichillustrates one method of the invention.

FIG. 12 is a graph of the RSSI signal as a function of time whichillustrates a second method of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides methods and apparatus for implementing awireless communication system that allows all of the system's componentsto operate under one system control unit so that the various componentscan adjust and adapt to the changes that occur in other components andthat improves the efficiency of communication over the wirelesscommunications network. In the following detailed description, numerousspecific details are set forth such as detailed block diagrams andsignal flow charts to provide a thorough understanding of the presentinvention. It will be appreciated, however, by one having ordinary skillin the art that the present invention may be practiced without suchspecific details. In other instances, well-known control structures andgate level circuits have not been shown in detail so as not to obscurethe present invention. Those of ordinary skill in the art, once providedwith the various functions below, will be able to implement thenecessary logic circuits without undue experimentation.

Now referring to FIG. 4, a wireless communication system 91 is presentedaccording to the present invention. Wireless communication system 91includes a system control unit 93 for controlling various components ofwireless communication system 91 and a data unit 97 for processing datasignals received from a computer host or data signals received from adigitally implemented cellular transceiver 96. Wireless communicationsystem 91 further includes an audio unit 108 for processing audiosignals that are received from digitally implemented cellulartransceiver 96 or that are to be transmitted to digitally implementedcellular transceiver 96. Digitally implemented cellular transceiver 96receives data signals from data unit 97 or audio signals from audio unit108. D/A & A/D converter 98 includes a D/A circuitry and an A/Dcircuitry. The D/A circuitry is used to convert signals in a digitaldomain into analog cellular signals. The A/D circuitry is used toconvert analog cellular signals received from radio transceiver 100 intodigital signals. Radio transceiver 100 is used to either transmit radiowaves to a base station or to receive radio waves from the base stationutilizing two different types of channels--control channels and voicechannels.

Data unit 97 includes a host interface 92 for interfacing wirelesscommunication system 91 to a data terminal equipment (DTE) such as acomputer host and a data pump 94 for performing modem signal processing.Referring to FIG. 5, a high speed modem data pump 94 typically containsa data conditioning block 200, a modulator 202 and an adaptivecompensation block 204. Adaptive compensation block 204 performsadaptive receiver algorithms that adjust the parameters of data pump 94so that the parameters can be optimally matched to the characteristicsof a remote modem and transmission channel. The adaptive receiveralgorithms used in data pump 94 may include functional blocks such as anautomatic gain control 206, a timing interpolator 208, an equalizer 210,carrier phase tracking 212, etc. A demodulator function for data pump 94can be included in any of the functional blocks mentioned above (e.g.,automatic gain control 206, timing interpolator 208, equalizer, andcarrier phase tracking 212) or may be implemented as a separatefunctional block in 204.

Automatic gain control 206 compensates for the different signal levelsarriving at the data pump input, and presents reasonably stable inputlevels to the other functional blocks in 204. Very often the timingfrequencies of a remote modem's data pump in a transmission mode and thelocal modem's data pump in a reception mode are slightly different, andtiming interpolator 208 may need to adaptively adjust the local timingso that it is identical to the remote timing. Equalizer 210 adaptivelycompensates for the transmission channel amplitude and delaydistortions. Carrier phase tracking 212 adaptively corrects errors thatoccur due to the differences between the local modem's data pump timingand the carrier frequency timing of the remote modem's data pump.

Audio unit 108 includes a microphone 104, a speaker 106 and anencoder/decoder (CODEC) unit 102. Microphone 104 receives acoustic wavesand converts them into electrical audio signals. Speaker 106 receiveselectrical audio signals, converts them into acoustic waves andtransmits the acoustic waves into the air. CODEC unit 102 is used toencode or decode signals using a non-linear conversion function such asthe m-law or A-law or a linear conversion function.

Digitally implemented cellular transceiver 96 processes either digitaldata signals or audio signals. Because digitally implemented cellulartransceiver 96 processes signals in the digital domain, no D/A & A/Dconverter is required between data unit 97 and digitally implementedcellular transceiver 96. Because there is no digital to analogconversion between data unit 97 and digitally implemented cellularprocessor 96, there is less degradation in signal quality.

Now referring to FIG. 6, digitally implemented cellular transceiver 96includes a first block 111 that performs cellular signaling protocols tocommunicate with the base station and a second block 113 that performssignal conditioning to communicate with a remote unit through the basestation. In the first block 111, digitally implemented cellulartransceiver 96 processes various cellular signaling protocols such asdotting patterns, signaling tone (ST) generation, signaling patterndetection and generation, and manchester coding/decoding. Digitallyimplemented cellular transceiver 96 also handles other cellularsignaling protocols such as controlling different phases of callestablishment, hand-offs, and termination. It should be noted thatdigitally implemented cellular transceiver 96 may process other cellularsignaling protocols not listed above. All cellular signaling protocolsare implemented on the same digital processor, or they run as a group oftasks under the same operating system or scheduler. While digitallyimplemented cellular transceiver 96 directs, generates and processes thecellular protocols, system control unit 93 determines when to send thesignals and what to do with the signals.

In the second block 113, digitally implemented cellular transceiver 96includes a CODEC driver 146 for interfacing the software functions ofdigitally implemented cellular transceiver 96 to CODEC unit 102. IfCODEC unit 102 uses a non-linear conversion function, then an encoder142 and a decoder 144 are implemented in digitally implemented cellulartransceiver 96. Decoder 144 is used to convert the non-linear signalsencoded by CODEC unit 102 into linear signals. Encoder 142 is used toconvert linear signals coming from a de-multiplexer 128 into non-linearsignals. If, on the other hand, CODEC unit 102 uses a linear conversionfunction, then encoder 142 and decoder 144 are not needed. The advantageof having a non-linear CODEC unit 102 is that it is generallyinexpensive. In the present invention, the disadvantage of having anon-linear CODEC unit is that it requires extra hardware: encoder 142and decoder 144. In addition, signals get degraded when encoder 142 ordecoder 144 converts the signals from one form to another.

The second block 113 further includes a multiplexer 140, a compressionunit 134, a pre-emphasis unit 132, a first filter 130, a second filter122, a de-emphasis unit 124, an expansion unit 126 and thede-multiplexer 128. Multiplexer 140 selects either the data signal fromdata pump 94 or the audio signal from decoder 144 (or CODEC driver 146if CODEC unit 102 is linear). Compression unit 134 manipulates a signalbased on its amplitude and is adjustable (or is software programmable)in that its characteristics can be adjusted depending on whether itreceives audio signals or data signals.

FIG. 7a shows one exemplary graphical relationship between an input andan output of compression unit 134 where the input is an audio signal.Compression unit 134 decreases the magnitude of the input signal if theamplitude of the input signal is low. On the other hand, compressionunit 134 increases the magnitude of the input signal if the amplitude ofthe input signal is high.

FIG. 7b shows one exemplary transfer function employed by compressionunit 134 where the input is a data signal. In this instance, compressionunit 134 uses a linear transfer function between the input and theoutput.

Referring back to FIG. 6, pre-emphasis unit 132 is used to manipulate asignal based on its frequency. Pre-emphasis unit 132 is also adjustable(or is software programmable) in that its characteristics may be varieddepending on whether it receives audio signals from the audio unit ordata signals from the data unit. First filter 130 is used to band-limita signal before it is sent to a transmit buffer 112 that is coupled tothe D/A circuitry in D/A & A/D converter 98. First filter 130 istypically a band-pass filter. Second filter 122 is used to receive asignal from a receiver buffer 110 which is coupled to the A/D circuitryof D/A & A/D converter 98. The characteristics of both first and secondfilters (130 and 122) can be adjusted depending on whether an audio ordata signal is being processed.

De-emphasis unit 124 manipulates a signal based on its frequency in amanner opposite to pre-emphasis unit 132. De-emphasis unit 124 is alsoadjustable (or is software programmable) like pre-emphasis unit 132.Expansion unit 126 manipulates a signal based on its amplitude in amanner opposite to compression unit 134. Expansion unit 126, in effect,is used to undo what a compression unit does. Expansion unit 126 is alsoadjustable (or is software programmable) depending on the type of inputsignal.

FIG. 8a shows a typical graphical relationship between an input and anoutput of an expansion unit used for audio signals. The transferfunction of FIG. 8a is substantially an inverse function of that shownin FIG. 7a. The transfer function shown in FIG. 8a increases theamplitude of its input signal if its amplitude is low, and decreases theamplitude of its signal if its amplitude is high.

FIG. 8b is a typical transfer function employed by expansion unit 126for data signals. The transfer function of FIG. 8b is substantially aninverse function of that shown in FIG. 7b. In this example, a linearfunction is employed for expansion unit 126.

De-multiplexer 128 is used to direct signals received from a singleinput to either data pump 98 or encoder 142 (or CODEC driver 146 ifCODEC unit 102 is linear).

It should be noted that the reason why the functional units in block 152(i.e., 122, 124, 126, 130, 132 and 134) can be adjusted (or is softwareprogrammable) depending on whether block 152 is processing audio or datasignals is that system control unit 93 in FIG. 4 controls all of dataunit 97, audio unit 108 and digitally implemented cellular transceiver96. System control unit 93 knows what type of signal is sent andreceived by various components, and it can adjust the characteristics ofthe components accordingly.

Referring to FIG. 4, in another embodiment, digitally implementedcellular transceiver 96 may be replaced by an analog cellulartransceiver. In that instance, D/A & A/D converter 98 is no longerneeded. However, a D/A & A/D converter is needed between data pump 94and digitally implemented cellular transceiver 96 so that during datatransmission, the digital signals from data pump 94 can be firstconverted into analog signals before entering into the analog cellulartransceiver, and during data reception, the analog signals from theanalog cellular transceiver can be converted into digital signals beforethe signals are sent to data pump 94. As described before, it ispreferable to place a D/A & A/D converter either at the beginning or atthe end of all signal processing. When the D/A & A/D converter is placedbetween two signal processing units (i.e., data pump 94 and the analogcellular transceiver), the signal quality deteriorates. Thus, an analogcellular transceiver is typically inferior in performance to a digitallyimplemented cellular transceiver.

The components such as data unit 97, digitally implemented cellulartransceiver 96 and system control unit 93 may be in one digital signalprocessing (DSP) chip, in one microprocessor chip, in a plurality of DSPchips or in a plurality of microprocessor chips. Whether wirelesscommunication system 91 uses a single chip or several chips, there willbe only one system control unit so that all the components can operateunder one operating system. Because the components such as data unit 97,audio unit 108 and digitally implemented cellular transceiver 96 areintegrated and operate under one operating system, information can bepassed between different components. Also, one component can adaptitself to the changes that occur in another component. For example, datapump 94 can adapt to impairments of the cellular line. Like a regularphone line, the cellular line can also have imperfection or distortions.When the characteristics of the control channels or the voice channelsof the cellular line change, because system control unit 93 controlsboth data pump 94 and digitally implemented cellular transceiver 96,data pump 94 can modify its parameters to compensate for the distortionthat occurs in the cellular line. Thus, because the various componentsare integrated and operate under one operating system, wirelesscommunication system 91 can achieve a higher transmission rate and/orlower error rate. Also, because the present invention is integrated,wireless communication system 91 can be put in one package, and thepackage can be much smaller than any of the conventional wirelesscommunication system packages.

FIG. 9a shows a flow chart illustrating one method of using controlchannel information to enhance data throughput of a wirelesscommunication system according to the present invention. Now referringto FIGS. 9a, 4 and 6, at step 302, digitally implemented cellulartransceiver 96 detects a control channel signal indicating that achannel interruption is to occur. The control channel signal includes adotting pattern and control channel message. At step 304, Manchesterdata decoder 114 decodes the control channel signal. At step 306, thedecoded control channel signal is sent to system control unit 93.

At step 308, system control unit 93 controls the parameters of theadaptive components of data pump 94 so that the parameters remain at aconverged state. The adaptive components include, but are not limitedto, an equalizer, a carrier phase tracking unit, an interpolator and anautomatic gain control unit. In the present invention, while there is nochannel interruption, the parameters of the adaptive components arecontinuously adjusted to adapt to the dynamic changes that occur in thecommunication channel. Conventionally, when there is a channelinterruption (e.g., a line drop), the parameters of the adaptivecomponents are lost. When the channel is reconnected, the adaptivecomponents have to be completely retrained. In the present invention,however, because there is only one system control unit (system controlunit 93) controlling all of the components (97, 96, 98, 100 and 108),when there is a channel interruption, system control unit 93 can commandthe adaptive components of data pump 94 to remain at its converged state(i.e., the last state before the channel interruption) so that when thechannel is reconnected, because the adaptive components are at the lastconverged state, it would take less time to re-train the components.During steps 302, 304 and 306, the parameters of the adaptive componentsare continuously adjusted. During steps 308, 310, 312 and 314, theparameters are maintained at the last converged state.

At step 310, system control unit 93 may send a command to a data pump ofa second modem so that the second modem can initiate an appropriateprocess to maintain the parameters of the adaptive components of thesecond modem at a converged state. At step 312, system control unit 93may send an acknowledgment of the control channel signal to the basestation. It should be noted that steps 310 and 312 are optional and thusneed not be executed, if so desired. At step 314, the channel isinterrupted, and data transmission stops. After detecting the controlchannel signal at step 302, digitally implemented cellular transceiver96 has about 100 msec to perform the steps 304-312 before the channel isinterrupted. At step 316, the channel is re-established so that the datacan be transmitted again. Because the parameters of the adaptivecomponents of the data pump were at the last converged state, the amountof time required to re-train the adaptive components is reduced.

FIG. 9b shows a flow chart illustrating another method of using controlchannel information to enhance data throughput of a wirelesscommunication system according to the present invention. Now referringto FIG. 9b, the steps 402-406 and 510-516 are the same as the steps302-306 and 310-316 of FIG. 9a, and thus the descriptions are notrepeated. At step 408, instead of merely having the parameters of theadaptive components remain at the last converged state, the parameterscan be continuously adjusted throughout the channel interruption periodso that when the channel is re-established, data pump 94 need not bere-trained. The wireless communication system 91 may track the rate ofparameter variations in the adaptive components of data pump 94 and/ormaintain the adaptive variations at the tracked rate (e.g., tap update,frequency offsets, etc.). The parameters of the adaptive components areadjusted during steps 402-516. FIG. 10 shows a computer system that mayutilize a wireless communication system in accordance with the presentinvention. A computer host 1000 includes a memory 1008 and a centralprocessor 1002. Memory 1008 and central processor 1002 are thosetypically found in most general purpose computer and almost all specialpurpose computers. In fact, these devices contained within computer host1000 are intended to be representative of the broad category of dataprocessors and memory. Many commercially available computers havingdifferent capabilities may be utilized in the present invention.

A system bus 1016 is provided for communicating information. A displaydevice 1010 utilized with the computer system of the present inventionmay be a liquid crystal device, cathode ray tube or other display devicesuitable for creating graphic images and/or alphanumeric charactersrecognizable to a user. The computer system may also include analphanumeric input device 1012 including alphanumeric and function keyscoupled to bus 1016 for communicating information and command selectionsto central processor 1002, and a cursor control device 1018 coupled tobus 1016 for communicating user input information and command selectionsto central processor 1002 based on a user's hand movement. Cursorcontrol device 1018 allows the user to dynamically signal thetwo-dimensional movement of the visual symbol (or cursor) on a displayscreen of display device 1010. Many implementations of cursor controldevice 1018 are known in the art, including a track ball, mouse, pen,joystick or special keys on the alphanumeric input device 1012, allcapable of signaling movement in a given direction or manner ofdisplacement.

The computer system of FIG. 10 also includes a wireless communicationsystem 1019 of the present invention coupled to bus 1016 forcommunicating data to and from computer host 1000. Wirelesscommunication system 1019 may implement the system shown in FIG. 4. Alsoavailable for interface with the computer system of the presentinvention is a data storage device 1017 such as a magnetic disk oroptical disk drive, which may be communicatively coupled with bus 1016,for storing data and instructions. The computer system of FIG. 10 mayalso include a printer for outputting data.

An alternative embodiment takes advantage of the existence of TheReceived Signal Strength Indicator ("RSSI") signal. This signal isgenerated by all radio transceivers that conform to the AMPSspecification. In FIG. 4, it is radio transceiver 100. This signal is ameasure of the strength of the radio signal received by the transceiver.The RSSI signal is monitored by the system control unit 93 and istransmitted to the base station over the control channel. The RSSI isused by the logic of the base station to determine when to switch fromone cell to another. As a result, the RSSI is an excellent predictor ofwhen the data connection between the transceiver and the base stationwill be interrupted by the base station electronics for a cell change orwhen a null is reached due to external conditions such as multipathsignal cancellation. Thus, it may be used to freeze the actions of theadaptive components before it follows a fading radio signal so far downthat it will not be able to converge when the radio signal strengthreturns to a more normal level.

A decision to freeze the adaptive components is based on a value derivedfrom the RSSI signal. The derived value may be no more than theamplitude level of the RSSI signal at a point in time, or it may be avalue that reflects the trend of the RSSI amplitude over a specifiedtime. Such a trend value would take small fluctuations into account.FIG. 11 provides an example of a typical situation. FIG. 11 is a graphof the RSSI signal as a function of time. This graph is somewhat typicalof the RSSI in a traveling car. Referring now to FIG. 11, the Y axisrepresents signal strength. The X axis represents either time ordistance. As can be seen, RSSI signal 1100 experiences smallfluctuations at points 1102 and 1104. At point 1106, signal 1100 beginsto experience a gradual but steady decrease in amplitude due for exampleto external interference. At point 1108 the external interferencebecomes very severe and signal 1100 falls off precipitously. After thesubsidence of the external influence, signal 1100 reappears at point1110 which is much higher in amplitude than point 1108. Signal 1100 thenexperiences an additional small signal fluctuation at point 1112 andthen rises gradually back to its nominal value at point 1114.

The problem, of course, with this all too typical signal pattern is thatwhen there is a channel interrupt, such as from points 1108 to 1110, theadaptive components of the data pump must be completely retrained.Furthermore, if the signal amplitude at points 1108 and 1112 isconsiderably different than at point 1108, retraining takes a long timeand data throughput is reduced.

The simplest method of using the RSSI signal is to program systemcontrol unit 93 to freeze all adaptive components when RSSI signal 1100reaches a predetermined critical level such as voltage level V₁ reached1₁ System control unit 93 is also programmed to unfreeze the adaptivecomponents when RSSI signal 1100 is once again above amplitude level V₁.In FIG. 11, this occurs at 1₂ where the amplitude is V₂ In this instanceV₂ is not the same as V₁. The greater the difference between V₁ and V₂the longer it will take for the adaptive components to retrain. Thus, inthis instance, the difference between V₁ and V₂ while not zero, is muchsmaller than it would have been if the adaptive components had attemptedto follow the incoming signal all the way until it cut off at point1108.

A second method is illustrated in FIG. 12. Referring now to FIG. 12, thevalue of the amplitude of the RSSI signal V is sampled at regularintervals, t₁, t₂, . . . t_(n). If the value of V decreases at each of nconsecutive samples, the adaptive circuitry is frozen; where n is aninteger such as 2, 3 or 4 and is determined by either the manufacturer,the user or by an internal algorithm. The time interval between samplesmay be on the order of 10 milliseconds. In the case shown in FIG. 12, ifn is 3, then the adaptive components would be frozen at level V3(corresponding to the voltage level at the sample taken at time t₈)which is higher than the level at which the adaptive components werefrozen in the example of FIG. 11. And the small amplitude variations atlocations 1102 and 1104 would not have triggered a freezing of theadaptive components before it was necessary since V did not decrease for3 consecutive samples.

While the present invention has been particularly described withreference to the various figures and embodiments, it should beunderstood that these are for illustration only and should not be takenas limiting the scope of the invention. Many changes and modificationsmay be made to the invention, by one having ordinary skill in the art,without departing from the spirit and scope of the invention.

What is claimed is:
 1. A method of operating an integrated cellularcommunication system which communicates with a remote modem by radiowaves through a base station and the telephone network and wherein saidsystem includes a data pump component having an adaptive component thatadjusts the parameters of said data pump to match the characteristics ofsaid remote modem and the communication channel between said remotemodem and said integrated cellular communication system, said data pumpcomponent being operatively connected to a cellular transceivercomponent which is in turn operatively connected to a radio frequencytransceiver component and a system control unit operatively connected toeach of said components, and wherein said radio frequency transceivercomponent generates a RSSI signal, the method comprising the stepsof:monitoring said RSSI signal; comparing said monitored RSSI signalwith a predetermined value; freezing said adaptive component when saidRSSI signal and said predetermined value are in a specifiedrelationship; unfreezing said adaptive component when said RSSI is nolonger in said specified relationship with said predetermined value suchthat said parameters of said data pump are substantially the same as atthe time of freezing said adaptive component.
 2. The method of claim 1wherein said relationship between said monitored RSSI signal andpredetermined value is that said monitored RSSI signal is lower in valuethan said predetermined value.
 3. The method of claim 1 wherein the stepof freezing said adaptive component includes the steps of freezing anequalizer, a carrier phase tracking unit, an interpolator and anautomatic gain control unit.
 4. The method of claim 1 wherein saidcellular communication system is used over an advanced mobile phonesystem cellular network.
 5. A method of operating an integrated cellularcommunication system which communicates with a remote modem by radiowaves through a base station and the telephone network and wherein saidsystem includes a data pump component having an adaptive component thatadjusts the parameters of said data pump to match the characteristics ofsaid remote modem and the communication channel between said remotemodem and said integrated cellular communication system, said data pumpcomponent being operatively connected to a cellular transceivercomponent which is in turn operatively connected to a radio frequencytransceiver component and a system control unit operatively connected toeach of said components, and wherein said radio frequency transceivercomponent generates a RSSI signal, the method comprising the stepsof:sampling the amplitude of said RSSI signal at predetermined timeintervals; comparing the amplitude of said sample at an interval withthe value of the amplitude of said RSSI signal at the previous interval;and freezing said adaptive component when said amplitude decreases for nconsecutive time intervals; and unfreezing said adaptive component whensaid RSSI is no longer in said specified relationship with saidpredetermined value such that said parameters of said data pump aresubstantially the same as at the time of freezing said adaptivecomponent.
 6. The method of claim 5 wherein n is
 3. 7. The method ofclaim 5 wherein the step of freezing said adaptive component includesthe steps of freezing an equalizer, a carrier phase tracking unit, aninterpolator and an automatic gain control unit.
 8. The method of claim5 wherein said cellular communication system is used over an advancedmobile phone system cellular network.